DMOORE

It's not very likely to happen to both gaskets at the same time. Are you 100% sure the correct head gaskets were installed?



Darrell.

mrv8outboard

Were was the gasket failed? It sounds like it was ingesting a small amount of water prior to the over heat ( water jackets/ bad flappers). You can not compress water so the cylinder pressure rises and you get failures. Both sides though makes one wonder? It is possible the over heat issue was extreme. Make sure they pressure test the heads as well as checking the surface. Check your sea water pump, if that is smoked then you had an extreme over heat. ouch. Check the exhaust flappers ( they should be replaced any way after a good over heat). Check the exhaust system for water leaks into the exhaust side from the water side.

Also with that much heat and cylinder pressure the top half of the rod bearing and the bottom half of the main bearings have a tendency to flatten out (squish). So do not be surprised if your oil pressure is a little lower than before once it is back together. Use an oil primer to prime the engine oil system before the first restart.

Let us know how you are making out. Good Luck.

Ghostrider

Man I feel for you!

I blew a starter the other day and thought it was because of the compression! Someone mentioned Hydraulic Lock Up while I was complaining abou thow crap my starter was so I raced down to the work shop and got to work ripping the heads off...
The engine turned after I cleaned it all out, drained everything and dried things up. Fortunately for me, this happened on a hose so the water was fresh and clean.

Here's the Starter and here's what I found:

Itsallgood995

The head gaskets are the Felpro 17042 (.038-.042” Gen 5 & 6) which are slightly thicker than the stock. The original motor w/ the peanut heads had .027” gaskets. The gaskets failed between the cylinders.

The rubber coated exhaust flappers in the y pipe were intact & seem fine. Not brittle like it was overheated.

No sea pump but the impellor in the outdrive (king cobra) had some sand in it. The impeller itself had a couple cracked tips but overall was not trashed. The o-ring seal on the housing was bad.


Jaayteee “What happened was that the
engine "dieseled", (ran on) but kicked backwards,
water is then drawn back into the exhaust.”

Not knowing exactly what happened scares the crap out me but the “diseled” theory seems to make the most cense.

Ghostrider. Looks like we have the same problem. what caused yours?

Ghostrider

My own stupidity. Had the timing wrong on the distributor when going for start up after a cam / intake / carb swap. Finally sorted the carb out then when I went to start, she back fired due to timing, but was on the hose so when she spun the wrong way she took out the starter and flooded a couple of cylinders. I didn't notice or even think about it. I just checked the timing, adjusted the distributor and went to crank again. That's when I noticed the starter had crapped out.

I went home, posted on here about how crap my starter was and MER Performance rightfully suggested what might have been the root cause. I screamed back down to my workshop and tore the engine down to find that he was completely correct!

I've cleaned it all out, drained it, spun it, oiled it, drained, spun it and done it all over again just to be sure. Now I'm waiting on my new starter to put it all back together again and see if I can't screw something else up!

How's your coming along?

John

Itsallgood995

Got the head gaskets in Saturday & got the heads back on. Compression is back & consistant.

Cracked my Performer manifold trying to E-Z out a vacuum plug. Ordered a new Air Gap RPM which should be in tomorrow.

Installing Corsa diverters & fighting the rigging.

Should be up & running by the weekend.

What cam & manifold did you switch to? You were running the Air Gap & 731 cam correct?

Ghostrider

Sort of, I had a Victor Jnr Manifold and the 731 cam but I was using the stock cam for break in as the 731 cam hadn't arrived by the time I wanted to start. I've now got the 731 cam but I'm testing a Crower with similar numbers (lift and duration) to the 731 but it's only got 110 Deg LSA. I also just acquired a 741 to put in next but I need the correct lifters and to re-check my springs for that!

The Air-Gap is on now with a 2" spacer and the Holley 850 HP, when the new starter arrives, I'll let you know if it all works!

Good luck with yours, keep us posted!